Turning at lights, downshifted 4th to 2nd gear and suddenly power sterring went, also oil light and battery light came on.
I managed to straighten up, engine was still running, revved the engine and the lights went out and power steering was back.
Could this be power steering linked? I had a problem last year of noise and it was ps belt slipped off but as car warmed the belt was getting back into place.

It sounds like a very slippy drive belt, as that would account for the battery and power steering, as you know the alternator and ps are driven by the belt, it may have been the water light as apposed to the oil light aswell as tne water pump is drivebelt driven i think on that engine if its like mine, look under the bonnet with the engine off and look at the belt for fraying which would indicate rubbing, also check the grooves in the back of the belt for slicing, this would also indicate a little belt slip or jump, if it is the belt if its like mine its a stretchy belt so doesnt have a tensioner, check the belt tension with your finger, if its loose you will need a new one, if its got a tensioner then try tightening it up depending on how tight it is, although i would have thought you would hear the belt if it slipped that much, but definately check it it might be in a pretty poor state if its jumped or slipped that badly.

This is weird, the loss of ps has not happened again however a couple of other things have happened recently maybe cold weather related or not. 2 days ago starting ok in the morning the low fuel and water temp lights came on and the digital display dissappeared, rev of engine and all returned to normal, this morning mileage and clock display dissappeared and petrol guage showed empty when I know I had a good half tank, on revving the whole display seemed to reset with with it cycling through display as if it was a self test and again all returned to normal giving correct data.

I will stand by a slipping belt, my dashboard went a bit lairy when my battery went, this may be alternator related or perhaps your battery has given up, check the voltages cold and running and see what you get, I also take it that you have adequate coolant. But easiest check would 've the battery first.

I mean the coolant temperature warning may be because the belt is slipping on the water pump, have a look while the engine is running just after starting it and watch the belt for any excessive flex and slide, it should have no more than half an inch of play.